Former All Black fullback Leon MacDonald has announced his retirement from rugby after a long string of head injuries.

The long-time Crusaders regular suffered a concussion while playing for Kintetsu in a pre-season game in Japan last year, forcing him to call time on his playing career. He won 56 Test caps for New Zealand between 2000 and 2008 and is third on the caps list for All Black fullbacks behind Mils Muliaina and Christian Cullen.

MacDonald will continue his involvement with rugby after being appointed assistant coach of Tasman and will also manage the Nelson rugby academy.

The New Zealand Rugby Union (NZRU) has sanctioned and fined Chiefs loose forward Sione Lauaki for serious misconduct. Lauaki last month pleaded guilty in Hamilton District Court to a charge of assault stemming from an incident at a Hamilton bar.

Sentencing has been held over until next month but Lauaki on Tuesday appeared before an NZRU disciplinary hearing, being fined an undisclosed amount and handed a final warning. The former All Black has been cleared to continue playing.

"We take these matters extremely seriously but in this case there were a number of mitigating circumstances and we are comfortable that the incident itself was at the lower end of the scale," NZRU professional rugby general manager Neil Sorensen said. "However, Sione has a history of similar conduct and we have imposed a sanction which reflects that we have treated this matter seriously."

Lucas Amorosino, Jeremy Staunton and Joe Duffey have all signed new contracts with Leicester Tigers. The Pumas wing, former Wasps fly-half and ex-Nottingham hooker all joined the Tigers last summer and bolster their ranks following the departure of Lewis Moody and Sam Vesty to Bath.

Bulls lock Flip van der Merwe has signed a new contract with the Super 14 franchise until 2012.

Club officials at Marseille Vitrolles have been forced to deny reports of All Black legend Jonah Lomu's death from a heart-attack. The French third division club told The New Zealand Herald that their giant wing, capped 63 times by New Zealand, was alive and well following a rash of reports on social networking site Twitter.

Sharks prop Jannie du Plessis is free to continue playing after two citings for dangerous play in their win over the Reds were dismissed by a SANZAR disciplinary panel.

Gloucester youngsters Rupert Harden, Shaun Knight and Yann Thomas have signed new two-year deals with the Guinness Premiership club.

London Irish No.8 Chris Hala'ufia has been cited for a dangerous tackle on Wasps fly-half Dave Walder during their Guinness Premiership loss at Adams Park last weekend. Hala'ufia's case with be heard on April 14 .